Questions and exercises  are given by the computer, which decides ______ to move the students ahead, review an easier level, ____ give more work on the same level.

______ he had worked hard all the time, he failed the exam again. 

Jim came back early last night. It was not yet eight o'clock ________ he got home.

It is known to all that ____ you exercise regularly, you won’t stay healthy.

 We can't wait any longer ________ we'll miss the plane.